Measurements using Smart Phone Apps and the PU...

Measurements using Smart Phone Apps and the PU Probe

Vibro-Acoustics Consortium Web MeetingUniversity of Kentucky

Vibro-Acoustics Consortium

May 14, 2020


Overview

2

• Introduction

• Smart Phone Measurements Hardware and Software

• Smart Phone Measurements Level Tests

• Smart Phone Measurements Application Cases

• PU Probe Hardware

• PU Probe Engine Application

• PU Probe UAV Application

• PU Probe Radiation Efficiency

• Future Directions

Vibro-Acoustics Consortium 3

Sound and Vibration FieldsAn acoustic field implies a small disturbance. Sound pressure disturbances are only on the order of 1 Pa for 94 dB.

Wallin et al., 2011


Particle Motion

• Particles oscillate (but no net flow)• Waves move much faster than particles

https://www.acs.psu.edu/drussell/demos.html


Condenser Microphones

Bies, Hansen and Howard, 2018


MEMS Microphones

Diaphragm

Backplate Electrode

Substrate


Overview

7

• Introduction









LG Tribute DynastyiPhone 6 Plus iPhone 7 Plus

Smartphone Types

8


PCB 378B11Siemens DAQ

Mic-WBSWA

Internal Microphone

Microphones

https://www.engineering.com/ElectronicsDesign/ElectronicsDesignArticles/ArticleID/6124/How-MEMS-Enable-Smartphone-Features.aspx

9


Signal Scope XFaber Acoustical

iNVHBosch

Sound Meter XFaber Acoustical

NIOSH SLM

Smartphone Apps Used

10


Calibrate the PCB microphone

Calibrate the Apps

Measure in “free field”

Generate a 94 dB noise (measured by PCB microphone)

Mount the sensors together

Microphone Calibration

11



Mic-W

12


Overview

13

• Introduction










Test Setup

The Smart phone, Mic-W and PCB microphone are mounted directly above (1 m) the loudspeaker.

Smartphone and microphonesFree space measurement

1 m

14


Sound Pressure Level (dB)

Sound Meter PCB NIOSH PCB iNVH PCB

60.0 62.0 60.0 58.7 60.0 61.5

65.0 66.8 65.0 63.2 65.0 66.5

70.0 71.7 70.0 68.1 70.0 72.0

75.0 76.6 75.0 73.2 75.0 76.2

80.0 81.4 80.0 78.1 80.0 81.3

85.0 86.5 85.0 83.2 85.0 86.2

90.0 91.5 90.0 88.2 90.0 91.3

95.0 96.5 95.0 93.2 95.0 96.3

100.0 102.3 100.0 98.5 100.0 101.8

iPhone 6 Plus with Internal MicrophoneWhite noise source with internal microphones uncalibrated.

15



Sound Meter PCB NIOSH PCB iNVH PCB

61.5 62.0 58.2 58.7 61.3 61.5

66.5 66.8 63.2 63.2 66.3 66.5

71.5 71.7 68.2 68.1 71.3 72.0

76.5 76.6 73.2 73.2 76.3 76.2

81.5 81.4 78.2 78.1 81.3 81.3

86.5 86.5 83.2 83.2 86.3 86.2

91.5 91.5 88.2 88.2 91.3 91.3

96.5 96.5 93.2 93.2 96.3 96.3

101.5 102.3 98.2 98.5 101.3 101.8

iPhone 6 Plus with Internal MicrophoneWhite noise source with internal microphones calibrated.

16



Sound Meter

PCB SCADAS NIOSH PCB

SCADAS iNVH PCB SCADAS

60.7 60.2 60.5 59.9 63.0 60.2

65.4 65.2 65.3 65.2 66.0 64.8

70.2 70.1 70.0 70.0 70.0 69.5

75.0 75.1 75.0 75.1 75.0 74.6

80.0 80.0 80.0 80.0 80.0 79.4

85.0 85.1 85.0 85.0 85.0 84.4

90.0 90.2 90.0 90.0 90.0 89.6

95.0 95.2 95.0 95.0 95.0 94.6

100.0 100.1 100.0 99.9 100.0 99.5

iPhone 6 Plus with Mic-WWhite noise source with Mic-W calibrated with white noise.

17


Overview

18

• Introduction










Compressor Noise SPL Comparison

The smartphone, Mic-W and PCB microphone aremounted directly above the compressor.

Apps are calibrated using 94 dB @ 1 kHz.

SPL is in dB.

Free space

50 cmDevice Sound

Meter NIOSH iNVH PCB

Internal Microphone

(iPhone 7 Plus)85.2 83.6 85.2 86.7

Mic-W(iPhone 6 Plus) 85.1 83.4 84.8 86.7

19


The smartphone, Mic-W and PCB microphone aremounted directly above the compressor.

Apps are calibrated using 94 dB @ 1 kHz.

SPL in dBA.

Free space

50 cmDevice Sound

Meter NIOSH iNVH PCB

Internal Microphone

(iPhone 7 Plus)82.6 82.8 83.0 83.8

Mic-W(iPhone 6 Plus) 82.4 82.6 82.0 83.8

Compressor Noise SPL Comparison

20


• The Smartphone, Mic-W and PCB microphone are mounted adjacent to one another at the end of an impedance tube.

Impedance Tube SPL Comparison

21


PCB MicSiemens DAQ

Reference

Mic-WSignal Scope

LG Internal Mic Sound Meter

84.5 85 81

89.7 90 83

94.5 95 85

99.2 100 86

104.5 105 87

109.8 110 88

Impedance Tube SPL Comparison

White Noise Source

22


125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

1000

012

500

1600

0

Soun

d Pr

essu

re L

evel

(dB)

Frequency (Hz)

MicW + iPad miniPCB + SCADAS

Microphones are placed 1 m far away from Harley Davidson Engine (idle running).

10 dB

Motorcycle Engine SPL Comparison

23


Summary

Pros• Portable• Easy to use• Good accuracy below 10 kHz• Inexpensive

Cons• Issues at low frequency and low

sound pressure levels

24


Overview

25

• Introduction










P-U Probe

P-U Probe with Wind Shield

Hollow Cylinder

Pressure Inlet

PCB

Miniature Microphone

Solid Cylinder

Microflown Hotwire

Microflown PU Probe

26


Hot Wire

Heat Transfer

Resistance Changes

2 Hot Wires

Microflown PU Probe

27


Microflown PU Probe Calibration

1. Use microphone to calibrate pressure sensor.

2. Use 𝑍 to calibrate the sensitivity of the velocity sensor.

3. Use ∠𝑍 to calibrate the phase of the velocity sensor.

Impedance: 𝑍 𝜌𝑐𝑖𝑘𝑟

1 𝑖𝑘𝑟

28


Sound Pressure Sensitivity and Phase

29



Parameters Pressure𝑆 47𝑓 32𝑓 20𝑓 5848𝐶 28𝐶 37𝐶 200000

Sensitivity

Phase

𝑆mVPa 𝑆 @1 kHz

1 𝑓𝑓

1𝑓𝑓 1

𝑓𝑓

𝜑 deg arctan𝐶𝑓 arctan

𝐶𝑓 arctan

𝑓𝐶

30


Particle Velocity Sensitivity and Phase

31


Particle Velocity Calibration

Parameters Velocity𝑆 48000𝑓 63𝑓 633𝑓 97580𝑓 62𝐶 1𝐶 699𝐶 24000𝐶 50

Sensitivity

Phase

𝑆mVm 𝑠⁄

𝑆 @250 Hz

1 𝑓𝑓 1 𝑓

𝑓 1 𝑓𝑓 1 𝑓

𝑓

𝜑 deg arctan𝐶𝑓 arctan

𝑓𝐶 arctan

𝑓𝐶 arctan

𝐶𝑓

32


Sound Intensity Comparison

P-U Probe P-P Probe

30in

ches

33


Overview

34

• Introduction










36 Grid Locations

Motorcycle Engine Transmission

35


0 1000 2000 3000 4000 5000

Frequency (Hz)

Soun

d In

tens

ity (d

B)

P-U ProbeP-P Probe

700 Hz

1375 Hz

10 dB

Averaged Sound Intensity Comparison

36


P-U Intensity

P-U Velocity

P-P Intensity

Intensity and Velocity Mapping (700 Hz)

37


P-U Intensity

P-U Velocity

P-P Intensity

Intensity and Velocity Mapping (1375 Hz)

38


Overview

39

• Introduction










UAV Measured by P-U Probe

P-U Probe with wind screen

UAV on hovering: with blade ~5700 RPM

40


2000.00

0.00

Hz

15.000.00 s(Time)

85.00

20.00

dBm

/s(p

v)

Particle Velocity

UAV Measured by P-U Probe

41


Sound Pressure Levels

40

50

60

70

80

90

SPL

(dBA

)

Frequency (Hz)

Top surface Bottom surface

Sound Pressure

l

l

42


Near Field Measurement

20

30

40

50

60

70

80

90

0 100 200 300 400 500

SPL

(dB)

Frequency (Hz)

0102030405060708090

0 100 200 300 400 500So

und

Inte

nsity

Lev

el (d

B)Frequency (Hz)

176 Hz164 Hz

Sound Pressure Sound Intensity (P-U Probe)

Unlike microphone, P-U probe is able to filter out nearby source components.

176 Hz

43


10

100

1000

10000

0 1000 2000 3000 4000 5000

Impe

danc

e Am

plitu

de (P

aꞏs/

m)

Frequency (Hz)

Top surfaceBottom surface

Acoustic Impedance

Top and Bottom Impedance

Hollow Cylinder

Pressure Inlet

PCB

Miniature Microphone

Solid Cylinder

MicroflownHotwire

P-U Probe

44


Overview

45

• Introduction










Radiation Efficiency

= =

Force Transfer Function Vibration Radiation Efficiency Sound Power


46




𝜎 𝑊 𝑓

𝜌𝑐𝑆𝑢 𝑓

𝑊 𝑓 sound power emitted by the vibrating surface𝑆 vibrating surface area𝑢 𝑓 spatially averaged RMS value of velocity

47



ISO 7849 Measure Radiation Efficiency

ISO-7849 – Determination of airborne sound power levels emitted by machinery using vibration measurement -- Part 2: Engineering method including determination of the adequate radiation factor• Test 1 – Accelerometer Array for Surface Velocity• Test 2 – Intensity Scan for Radiated Sound Power

ISO/TS 7849-1:2009(E)

SourceTest 1

Test 2

Intensity Scanning

Accelerometer Point

48



Disadvantages• Accelerometers affect surface

vibration.• Requires two separate tests –

longer setup time.• Complicated structures may be

difficult to instrument.

Alternative – PU Probe• Both particle velocity and sound

power can be measured with same sensor using scanning approaches.

ISO/TS 7849-1:2009(E)

ISO 7849 Measure Radiation Efficiency

49



Surface Velocity Correction

distance

𝑎

𝑢𝐶

𝑢𝑎

𝑗𝜔

Calibration Constant (𝐶 )

Acceleration (𝑎 ) is sampled at a single location. Particle velocity (𝑢 ) may be sampled at a single location or multiple locations.

50



Aluminum Panel Test Setup

• The panel is divided into 16 patches andthe standard method was used as areference.

• Total sound power was measured by PUprobe.

• Panel driven by shaker with white noise

Size: 0.5 0.5 m2

Thickness: 3 mm

Position 10

51



0.001

0.01

0.1

1

10

200 2000

Squa

red

Velo

city

Rat

io

Frequency (Hz)

PU Probe 2 cmPU Probe 5 cmPU Probe 10 cm

Single position correctionReference: Position 10

Aluminum Panel Velocity Ratio

100 Hz running average applied to clean up data.

52



0.001

0.01

0.1

1

10

100

200 2000

Squa

red

Velo

city

Rat

io

Frequency (Hz)

PU Probe 2 cmPU Probe 5 cmPU Probe 10 cm

• 100 Hz running average applied to clean up data.

• Calibrated at 16 discrete positions.

Aluminum Panel Velocity Ratio

Note: Data is shown for illustration purposes but not used for radiation efficiency calculation.

53




0

20

40

200 2000

Velo

city

(m/s

)

Frequency (Hz)

PU Probe 2 cm

Accelerometer

Aluminum Panel Velocity

54



10

20

30

40

50

200 2000

Soun

d Po

wer

(dB)

Frequency (Hz)

Original

Averaged

Aluminum Panel Sound Power

55




0.001

0.01

0.1

1

10

100

200 2000

Rad

iatio

n Ef

ficie

ncy

Frequency (Hz)

PU Probe 2 cm

PU Probe 10 cm

Standard

Aluminum Panel Radiation Efficiency

56



Material: Aluminum

Size: 0.24 0.17 m2

Position 5

• The oil pan is divided into 9 patches andthe standard method was used as areference.

• Total sound power was measured by PUprobe.

• Oil pan driven by shaker with white noise.

Oil Pan Test Setup

57




0.01

0.1

1

10

100

200 2000

Rad

iatio

n Ef

ficie

ncy

Frequency (Hz)

PU Probe 2 cm

Standard

Oil Pan Radiation Efficiency

58



Overview

59

• Introduction











Future Directions

60

• UK will continue to investigate new measurement tools using smartphones.

• The PU probe may also be used for sound quality. The particle velocity can be converted to a .wav file and listened to.

• The PU probe may also be used for transient particle velocity measurements. This should have application to pass-by noise.



References

Smart Phone Microphones• L. L. Beranek and T. J. Mellow, Acoustics: Sound Fields and Transducers, Academic Press (2012).• D. A. Bies, C. H. Hansen, and C. Q. Howard, Engineering Noise Control, 5th Edition, CRC Press, Boca

Raton, FL (2018).PU Probe• H-E de Bree, P. Leussink, T. Korthorst, H. Jansen, T.S. Lammerink, and M. Elwenspoek, “The μ-Flown: a

Novel Device for Measuring Acoustic Flows”, Sensors and Actuators A: Physical, 54(1-3), 552-557 (1996).• H-E de Bree, “The Microflown, a New Particle Velocity Sensor,” Sound and Vibration Magazine, 39(2), 8,

(2005).• The Microflown E-book, Online, 2009.Standard Measurement Procedure for Radiation Efficiency• ISO/TS 7849-2, Acoustics — Determination of airborne sound power levels emitted by machinery using

vibration measurement — Part 2: Engineering method including determination of the adequate radiation factor, International Organization for Standardization, Geneva, (2009).

Radiation Efficiency Research at UK• S. C. Campbell, D. W. Herrin, B. Birschbach, and P. Crowley, “Measurement of Radiation Efficiency with a

Combination Sound Pressure – Particle Velocity Sensor,” Noise-Con 2019, San Diego, CA, August 26-28 (2019).

• S. C. Campbell, D. W. Herrin, B. Birschbach, and P. Crowley, Notes on Measurement of Radiation Efficiency, Inter-Noise 2018, August 26-29, Chicago, IL (2018).

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Measurements using Smart Phone Apps and the PU...

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